The present invention relates to the manufacture of electronic devices. More particularly, the present invention relates to improved techniques for preventing the corrosion of an aluminum neodymium-containing layer during the manufacture of electronic devices.
In the manufacture of certain types of electro nic devices such as flat panel displays and the like, an aluminum neodymium-containing layer may be employed. Aluminum neodymium is the material of choice for manufacturing these devices due to its superior chemical and physical properties. But as with all aluminum alloys, corrosion remains a significant problem in the processing of aluminum neodymium in spite of its superior material characteristics.
Aluminum neodymium is generally etched with chlorine which results in residual chlorine adhering to the etch surface. When this etch surface comes in contact with the atmosphere, the residual chlorine reacts with moisture in the air to form hydrochloric acid. This hydrochloric acid eats away at the metal, which results in corrosion of that metal. The fundamental approach to resolving this problem is to remove the residual chlorine to prevent the formation of corrosive substances such as hydrochloric acid. Conventionally, this is accomplished by the use of a gas chemistry having CF.sub.4 and oxygen. However, when CF.sub.4 and O.sub.2 are applied to prevent corrosion of aluminum neodymium, the high chlorine content in conjunction with the high ion energy required for the processing of this sturdy material requires a high ion energy level during removal of the residual chlorine. This in turn results in severe damage to the photoresist layer, which is an undesired side effect of the corrosion prevention process. Photoresist damage usually translates into hardened photoresist fragments on the substrate surface, which is harder to strip off in the later step of the manufacturing process. It is believed that high ion energy is necessary to remove the residual chlorine because high ion energy is used in the main etch, which results in the chlorine ions being embedded further in the etched surface than a conventional process where lower ion energy is used.
FIG. 1 illustrates the corrosion problem occurring in an exemplary layer stack 100. Layer stack 100 has an aluminum neodymium-containing layer 102 disposed above a substrate 104, which may be, by way of example, glass. It should also be noted that the devices of the figures shown herein are depicted in a simplified format for illustration purposes only. There may be present other additional layers above, below, or in between the layers shown. Further, not all of the shown layers need necessarily be present and some or all may be substituted by other different layers. The layers of the devices shown and discussed herein are readily recognizable to those skilled in the art and may be formed using any of a number of suitable and known deposition processes, including chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and a physical vapor deposition (PVD), such as sputtering.
An optional molybdenum layer 106 is disposed above aluminum neodymium-containing layer 102 and below a photoresist layer 108. Molybdenum layer 106 is not essential to the invention, but is included to show an example of a corrosion problem where an aluminum neodymium-containing layer is contained within a sandwich structure. A sandwich structure, for example, an aluminum neodymium-containing layer encapsulated in refractory metals such as molybdenum, is typically used to prevent hillock formation that might occur during processing steps and device operation. A refractory metal is a metal having an extremely high melting point, for example, tungsten, molybdenum, tantalum, niobium, and chromium, vanadium, and rhenium. In a broad sense, this term refers to metals having melting points above the range for iron, cobalt, and nickel. However, sandwich structures are often very prone to corrosion, in fact, the severity of corrosion problems in a sandwich structure is greater by orders of magnitude compared to the corrosion problem of an aluminum neodymium-containing layer that is not within a sandwich structure.
The chlorine component in the etchant gas chemistry adheres to the etched surface 110 and forms hydrochloric acid when it comes in contact with moisture in the air. The hydrochloric acid reacts with the aluminum neodymium-containing layer to cause corrosion as shown in exposed portion 112 of aluminum neodymium-containing layer 102.
FIG. 2 illustrates the situation where an exemplary layer stack 200 having an aluminum neodymium-containing layer 202 disposed below an optional molybdenum layer 204 and above a substrate 206 is treated by the traditional method of using CF.sub.4 and O.sub.2 to prevent corrosion. While corrosion is successfully prevented, the process has the unfortunate side effect of severely degrading the photoresist layer 208. Severe degradation of photoresist layer 208 may cause unwanted hardening of the photoresist material, which makes subsequent removal of photoresist layer 208 very difficult. Moreover, some of the hardened resist may deposit on sidewalls and other areas, masking certain regions that were designated to be unmasked for the purpose of etching, which causes the formation of jagged sidewalls 210 along aluminum neodymium-containing layer 202 and molybdenum layer 204 as well as severe residue problems.
In view of the foregoing, what are desired are improved methods for preventing corrosion in an aluminum neodymium-containing layer. These improved techniques preferably would prevent corrosion along the etched surface of the aluminum neodymium-containing layer while avoiding problems such as severe degradation of the photoresist layer which might lead to other serious problems.